Photographic product and process for making a positive transfer image



E. H. LAND PHOTOGRAPHIC PRODUCT AND PROCESS FOR MAKING A POSITIVE TRANSFER IMAGE Filed Feb. 8, 1947 Image Carrying Layer,

Confcxiner FIG. I

INVE TOR United States Patent ()fiiice 2,698,245 Patented Dec. 28, 1954 Edwin H. Land, Cambridge, Corporation, Cambridge, ware Application February 8, 1947, Serial No. 727,385 13 Claims. (Cl. 95-88) Mass., assignor to Polaroid Mass., a corporation of Delaphotography and more parphotographic processes and products This invention relates to ticularly to novel for use therewith.

A principal object of the present invention is to provide a photographic process for obtaining an improved positive silver image from a latent negative image contained in a layer of a silver halide photosensitive material.

Another object of the present invention is to provide an improved photographic product for use with the above process.

Still another object of the invention is to provide improved positive image-forming processes particularly adaptable for use With the fast films.

Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the product possessing the features, properties and the relation of components, and the process involving the several steps and the relation and the order of one or more of such steps with respect to each of the others which are exemplified 'in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein:

Figure 1 is an exaggerated diagrammatic cross-sectional view of a preferred modification of the product of the invention.

In general this application relates to improvements in positive image-forming reactions of the type wherein a latent negative image is formed in a silver halide photosensitive layer, the latent image is developed, and, concurrently with this development, soluble silver complexes are formed with undeveloped silver halide and these complexes are transferred to an image-carrying layer where they are converted to particles of silver forming the positive image. In such processes, the above steps are preferably accomplished by spreading a viscous solution of a film-forming material, a developer and a silver halide solvent between the photosensitive layer and the imagecarrying layer, to form a lamination having a dry exterior and within which said positive image-forming reaction may take place.

It has been found that the above positive image-forming reaction may be accelerated and improved to give a positive image having an increased gamma, density, and contrast by using precipitation nuclei to aid in the conversion of the soluble silver complexes to particles of silver. This effect is particularly noticeable where the silver halide photosensitive layer, such as is found with the fast films, for example, Ansco Triple S Pan, and Kodak Verichrome, contains a relatively high percentage of silver iodide, (or bromiodide) in comparison to the bromide and chloride paper emulsions.

In addition to improving the quality of the positive image, the precipitant nuclei have definite utility in predetermining the particular stratum of the lamination in which the positive image is primarily formed.

If dark brown to black images of good contrast are to be obtained there should be no more than about 10 separate, ungrouped. precipitation nuclei per cc. in the stratum of the positive image. If a single ion is used as a precipitant nucleus, the concentration of the ions per cc. of the positive image stratum reaches an impractically low figure in the neighborhood of one part in 10 billion.

If more than about 10 separate, ungrouped, precipi tation nuclei per cc. are present, there will be so many places for the silver to start precipitation that the grains will not grow to full desired size (about /2 micron) using the amount of silver brought down by the solvent. As this amount of silver is increased it will darken the grains in the shadows, making them black or dark brown, will increase the size of the silver grains in the middle tones to change their color from light yellow to dark yellow and will yellow the highlights. When the size of the middle tone grains is enlarged to black by further growth, the highlights are further darkened and all detail is removed from the shadows.

In the present process, positive images of substantially uniform color for all tone gradations are achieved by 1) providing nuclei in no greater concentration than 10 per cc. and (2) adjusting the effective size of such nuclei so that when silver aggregates appear visible on the nuclei they will be brownish or gray, this effective size being in the neighborhood of /2 micron. These two effects are achieved by employing precipitation n-uclei comprising crystals, aggregates of crystals or aggregates of ions of such size as to be conveniently handled quantitatively.

These crystals may be of several types. Where the crystals have a low optical absorption coefficient they may be relatively large, /2 micron or larger). When the crystals have a high optical absorption coefficient they must either be so small, and in such low concentration, as to absorb no substantial quantities of light in the highlights, or they must be capable of being bleached by the liquid composition in the highlights.

When the very small crystals of a high optical absorp tion coefficient are employed as nuclei, their actual size must be smaller than /2 micron to give low apparent optical absorption and their effective size must be increased to about /2 micron to give dark silver particles. One way of increasing the effective size of the crystals is to form galaxies of these crystals, the mass density of the galaxies being so low that little or no optical density is apparent. Another way of increasing their effective size is by allowing these individual crystals to dissolve slowly in the liquid composition, the effective size of the crystal being defined by the sphere of dissolving ions.

In general the size of the precipitant nuclei may be controlled in several ways. When the precipitant nucleus comprises a single crystal, its size may be controlled by precipitating the crystals under controlled conditions of temperature, of precipitation medium, of pH, reprecipitating the crystals from solution by sequential baths, or dissolving crystals of a size smaller than those desired. These procedures are particularly suitable for -those single crystals which are smaller than /2 micron. Where the crystals are of a larger size, in the neighborhood of /2 micron and larger, they may be additionally subjected to mechanical treatment such as occurs in a colloid mill and it is sometimes practical to separate various desired sizes of crystals by selective filtration.

When galaxies of extremely small crystals are to be employed these galaxies may be aggregated to the proper size by concentrating them in the spaces between inert particles suspended in a liquid. Another way of forming a precipitant nucleus in the form of a galaxy, is to adsorb the precipitant anions to the surface of an inert adsorptive colloid. Still another method of forming such a galaxy is to impregnate minute plastic globules with precipitant anions which are only slowly released from the plastic globules.

Still another method of forming a nucleus, which acts as a precipitant nucleus. is to provide a cluster of cations which by reaction with the silver complex, frees the silver ions in the region of the cation cluster, for reduction and condensation into metallic silver. In general the clusters of cations are obtained as discussed above and, with some materials, the precipitant nucleus may comprise a cluster of anions and cations, both ions being effective to assist in the breaking up of the silver complex.

In a preferred form of the invention the precipitant nuclei are formed on the surface of the image-carrying layer. These anions in the nuclei are preferably sulfides or selenides, and are preferably those of the metals, their particle size being related to their color and solubility as outlined above. The cations are preferably those of the heavy metals and in particular thoseof -lead.

Referring now to Fig. 1 there is shown one modification of a preferred type of film unit for use with the present invention. As shown in cross-section in Fig. 1 the film unitcomprises a transparent base layer carrying'on one surface thereof a layer 12 of a silver halide photosensitive emulsion. There is also included an opaque imagecarrying layer 14. Positioned for discharge of its contained liquid between the photosensitive layer 12 and the image-carrying layer 14 is a container 16. Preferably included in the container 16 is a viscous aqueous alkaline solution of a developer and a silver halide solvent.

The base layer 10 is preferably made of a suitable film base .material such as;a cellulosic ester or mixed ester, such as cellulose nitrate, cellulose acetate, cellulose acetate propionate. or other substances capable of supporting a photosensitive emulsion. This base can be made opaque, if desired, by addition of suitable dyes or pigments to the above-named substances-or the base can be madeof paper and other materials suitable for carrying a photosensitive emulsion. The photosensitive layer 12 is preferably an emulsion of a silver halide and in particular, an emulsion which is high in silver iodide, or silver bromiodide content, .such as that sold by the Eastman Kodak Company, under the trade-mark Verichrome.

The image-carrying layer 14 in a preferred embodiment .comprises a sheet of paper known in the art as baryta :paper, which comprises a paper having thereon a gelatin coating including colloidal barium sulfate.

The image-carrying lever 14 may also be formed of many other materials. This layer is preferably permeable to a substance contained in the liquid composition, although this permeability is not absolutely essential, particularly if there is a permeable coating applied to the surface thereof. The image-carrying layer 14 may also be made of gelatin, regenerated cellulose, polyhydroxy alkanes, for instance, polyvinyl alcohol, sodium alginate, certain of the cellulose ethers such as methyl cellulose and their derivatives such as sodium carboxymethyl cellulose -or hydroxyethyl cellulose, carbohydrates such as gums or starch and mixtures of these materials where the latter are compatible.

The image-carrying layer 14, in one preferred embodiment of the invention has a coating of particles of an inert substance having sulfide ions adsorbed on the surface of the particles. This coating is preferably on the inner surface (i. e., that surface closest to the photosensitive layer) asset forth in the following nonlimiting example:

Example 1 3 grams of micropulverized silica aerogel (Santocel C, Monsanto) are added to 28 cc. of a 1% sodium sulfide solution and thoroughly mixed. This mixture is applied in a very thin coat to the surface of the image-carrying layer 14.

The liquid composition in the container 16, in its preferred embodiment, comprises a developer such as hydroquinone. a silver halide solvent such as sodium thiosulfate, and a film-forming substance such as sodium carboxymethyl cellulose which acts to form a dimensionally stable layer when spread between layers 12 and 14. There are also preferably included other substances to aid in the photographic reaction, such as a preservative, i. e., sodium sulfite, and an alkali, i. e., sodium hydroxide, plus water, tocarry the above-mentioned elements in solution. A suitable liquid composition may be prepared by thoroughly mixing the materials shown in the following nonlimiting example:

Example 2 Grams Water 1860 Sodium carboxymethyl cellulose 93 Sodium sulfite 78 Sodium hydroxide 74.6 Sodium thiosulfate 14.5 Citric acid 38.5 Hydroquinone 52.0

Various equivalents may be used in the above-mentioned liquid composition and it is equally possible to substitute for the film-forming sodium carboxymethyl cellulose, other film-forming materials such as other alkali-inert, water-soluble polymers, for example, by? droxyethyl, cellulose, the sodium. salt of polymethacrylic acid, and aluminum carboxymethyl cellulose. Equally, other developers, preservatives, alkalies, and silver halide solvents may be used, and other substances such as restrainers may be added where desired.

The container 16 is preferably formed of a substance such as an oxygen and water-vapor impervious material such, for example, as a sheet of wax-impregnated metalcoated paper, wax-coated metal foil, or a metal foil coated with a resin such as polyvinyl butyral which is inert to alkalies.

In the useof the film unit of Fig. 1 the photosensitive layer 12 is exposed to a subject image by light passing through the base layer 10. The processing of the film unit is next preferably accomplished by applying a mechanical stress to the film unit for the purpose of releasing the liquid composition from the container 16 and spreading it in a uniform thin layer between the image-carrying layer 14 and the photosensitive layer 12. Such processing can be most readily accomplished by passing the film unit through a pair of pressure rollers, the container end of the film unit passing through the rollers first. When the liquid composition is spread between the photosensitive layer 12 and the image-carrying layer 14, the developer solution develops a latent negative image and the sodium thiosulfate dissolves the undeveloped, unexposed silver halide grains and forms therewith soluble silver complexes. The soluble silver complexes migrate to the image-carrying layer, where they combine with the sulfide ions to form silver sulfide around which the remainder of the silver grains, constituting the positive image, are precipitated by the reducing action of the developer. In view of the slow dissolution of the sulfide, the positive image formation is concentrated primarily in the stratum of the formed lamination containing the sulfide. ions. This is true, even though the gelatin of the baryta image-carrying layer is a better protective colloid than the sodium carboxymethyl cellulose of the liquid layer.

The resulting positive image has been found to have good blacks, browns and whites due to the size of the silver grains constituting the positive image, the individual grains being large enough to absorb substantially all through the spectrum of visible light. This grain size seems to be determined by the fact that the sulfide ions are absorbed on the surface of the colloidal silica aerogel and therefore the silver grains are formed along and around the colloidal particles of silica aerogel. The optical phenomenon resulting from the use of this silica aerogel is very apparent, since if sodium sulfide is used alone on the image-carrying layer without being aggregated in large galaxies, or crystals, it gives an image having poor blacks, with yellow middle tones, the yellow color being attributed to the extremely small size of the silver grains formed where the sulfide ions are uniformly distributed over the whole image-carrying layer.

The image-carrying layer of Example 1 may be improved to give good gray middle tones by dipping the baryta sheet, before application of the mix, in a bath containing by weight 10% cadmium acetate, 1% neutral lead acetate, and 30% zinc nitrate. The time of this dip is about 30 seconds to 2 minutes, the sheet being stretched around a drying drum as it comes out of the bath. This sheet may also be dipped for 30 seconds, in baths containing, for example, 10% cadmium acetate, or 30% zinc nitrate and 10% cadmium acetate, or 30% zinc acetate. The middle tones with the latter baths range from dark brown to gray. The above baths also improve the stability of the positive image.

Other methods of preparing a positive image-carrying layer in accordance with the present invention are set forth in the following nonlimiting examples:

Example 3 10 cc. of a 10% solution of lanthanum chloride is mixed with 10 cc. of a 1% solution of sodium sulfide. The mixture is allowed to stand for a few hours and small quantities of the resulting precipitate are rubbed into the surface of an image-carrying layer comprising a sheet of baryta paper.

Example 4 10 cc. of a 10% solution of palladium chloride is mixed with 10 cc. of a 10% solution of sodium sulfide. The

resulting precipitate is used in the. same mariner as Example 3.

- solution containing by weight 1% The stability of a positive image formed on an imagecarrying layer of the type described in Examples 3 and 4 is improved if the baryta sheet is dipped, before the application of the metal sulfide, in a bath containing one or more metal salts capable of forming a relatively insoluble metal hydroxide. Such a bath may comprise a water neutral lead acetate, cadmium acetate and 30% zinc nitrate.

Other metallic sulfides which have been found to be particularly suited for use as precipitant nuclei are the lead, nickelous, cobaltous, and ferric sulfides. Equally, other metal sulfides may be used but are less preferred.

When galaxies of minute particles are to be formed for the purpose of serving as precipitant nuclei they are preferably formed in the presence of an inert colloid such as silica aerogel, bentonite, diatomaceous earths such as kieselguhr, Celite and Super Floss, powdered glass and fullers earth. Several nonlimiting examples of such .mixtures are set forth below wherein the materials are preferably added in the order indicated, are thoroughly mixed in a mechanical mixer, and the resulting mixture is rubbed into the surface of an image-carrying layer.

Example 5 24 cc. of a 10% solution of lanthanum chloride 4 g. of silica aerogel (Santocel C) 6 cc. of a 1% solution of sodium sulfide Example 6 24 cc. of a 10% solution of palladium chloride 4 g. of silica aerogel (Santocel C) 4 cc. of a 1% solution of sodium sulfide Example 7 40 cc. of a solution of nickelous chloride 7.5 g. of silica aerogel cc. of a 1% solution of sodium sulfide Example 8 96 cc. of a 20% solution of cadmium acetate 15 g. of silica aerogel 30 cc. of a 1% solution of sodium sulfide Example 9 20 cc. of a 37.5% solution of zinc nitrate 7.5 g. of silica aerogel 30 cc. of a 1% solution of sodium sulfide Example 10 48 cc. of a 40% solution of magnesium acetate 7.5 g. of silica aerogel x 15 g. of silica aerogel 30 cc. of a 1% sodium selenide solution Example 12 96 cc. of a 40% neutral lead acetate solution -15 g. of silica aerogel 30 cc. of a 1% sodium selenide solution 10 cc. of a 10% nitric acid solution The powdered inert material seems to have the ability to protect the galaxies of metallic sulfides and selenides from rupture during application of the mix to the imagecarrying layer.

When a large transparent, white, or colorless crystal is used as the precipitant nucleus it may be applied directly to the image-carrying layer, or, if it is sufliciently insoluble in the liquid composition, may be mixed in the liquid and spread as a dispersion therein.

When large relatively insoluble particlesare used they may comprise substances such as zinc sulfide which seem to acquire a coating of silver from the silver ions in the complex or released from the complex. It seems that the silver replaces the Zinc in the surface of the Zinc sulfide even though the Zinc sulfide is not appreciably dissolved in the liquid. An example of the one way of using zinc sulfide in the liquid composition is set forth in the following nonlimiting example:

Example 13 grams 'ofzincsulfide is added to 20 cc. of aliquid composition of the type described in Example 2 above.

When the large particle is a readily soluble substance such as lead acetate it must be used on the image-carrying layer rather than in the liquid composition. In such a case the cation seems to have the important silver concentrating function and it is believed that this is due to the presence of the cloud of cations released as the particle is dissolved, these cations releasing silver ions from the complex for reduction and condensation. Several examples of how these large soluble crystals may be placed on the image-carrying layer are set forth below:

Example 14 Powdered lead acetate is sifted through a 200 mesh screen and rubbed into the surface of a baryta imagecarrying layer.

Example 15 Powdered nickelous acetate is sifted through a 200 mesh screen, rubbed on a baryta image-carrying layer and used with a liquid composition having twice as much sodium thiosulfate as the liquid of Example 2.

Several metal salts appear to release cations and anions both of which are effective for breaking up the silver complex. Of these salts lead sulfide and lead selenide are preferred.

Several nonlimiting examples of methods of incorporating these salts on the surface of the image-carrying layer are set forth below:

Example 16 A sheet of baryta paper is dipped in a /6% bath of neutral lead acetate for seconds, squeegeed, and then dipped in a bath of ,4 sodium sulfide for 4 seconds.

Example 17 A mix is prepared from the following ingredients and 'then spread on the image-carrying layer in a thin coat.

96 cc. of a 40% water solution of neutral lead acetate 15 g. of silica aerogel 30 cc. of a /2 solution of sodium sulfide 18 cc. of a 15 solution of ascorbic acid 96 cc. 40% NLA 15 g. of silica aerogel 30 cc. water It has also been found that a readily soluble sulfide can be used on the image-carrying layer to give black shadows and brown intermediate tones if the sulfide is included on the image-carrying layer in relatively large, widely spaced crystals. This form of the invention may be practiced as set forth in the following nonlimiting example:

Example 19 /1 gram of sodium sulfide is dissolved in cc. of methanol. This solution is added to 50 cc. of acetone. The resulting precipitate is decanted and brushed on the surface of the image-carrying layer. Superior results are obtained if the image-carrying layer is prepared for receiving the sodium crystals by dipping for about 30 seconds in a bath containing by weight 10% cadmium acetate, 1% neutral lead acetate and 36% zinc nitrate.

When a selenide is used it may be in a form such as lead selenide or it may be in the form such as sodium selenide. The lead selenide is shown in Examples 11 and 12. Several examples of its use in the sodium selenide form are shown below:

Example 20 A 1% solution of sodium selenide is prepared. A baryta sheet is then dipped in this solution for about a minute, or the solution is rubbed into the surface of the baryta paper.

7 Example .21

3 "grams of "silica aerogel is added to '50 cc. of a 1% sodium selenide solution and thoroughly mixed. The resulting mix 'is rubbed onto a baryta image-carrying layer.

The image-carryinglayers of Examples 20 and 21 give good 'blacks and whites, with the middle tones varying "from reddish brown to gray.

While the above products and processes have been described in their preferred forms, numerous modifications thereof may be made within the-scope of the present invention. For example .the various elements of the liquid composition may be included in the various layers of :the film unit inposition :to be dissolved by theiliquid as it is spread between the two layers of the film unit. In some cases this arrangement of the active ingredients is quite desirable. This is particularly true in the case of .the sodium thiosulfate which may be partially or totally included on the image-carrying layer. In some cases, where the .thiosulfate complex is used cyclically the positioning of .the sodium thiosulfate enables the development of the negative to getslightly ahead of the dissolution of the unexposed silver halide and permits the retention of clear highlights even though the total quantity of .hypo used in'the'process is sufiiciently'high that'it would darken these highlights if it were in-the liquid composition and theother conditions were the same.

The ability of the precipitants described in the preceding examples to predetermine the stratum of the formed lamination in which'the positive image is created, has an important advantage. It permits the layer of liquid composition to be stripped from the positive image after the positive image has been formed thereby tremoving the majority of components of the liquid composition which might stain the positive image. This assists in .maintaining the stability of the positive image with respect to strong radiation, high humidity, and high temperature.

The-expression sulfide as'used in the .attached claims is intended to indicate a binary compound "of bivalent sulfur or a binary compound of sulfur which contains more sulfur than is required 'by the normal valency of the metal.

The expression relatively slowly should be interpreted in the light of the speed of the process involved, which may vary from as little as Sseconds to as much as 1-to'2 minutes.

The expression image-carrying layer, as used in the specification and the claims, refers to a layer adapted to receive a positive image in or on its surfaceor to support a layer which contains an image in or on its surface.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

-l. A photographic product comprisinga photosensitive element which includes a silver halide layer, a printreceiving element for receiving by transfer a positive print, and a rupturable containing means holding aliquid, said product having positioned therein photographic reagents including a silver halide developer and a silver halide solvent, said containing means and said elements being so held together that said containing means is capable, upon rupture, of releasing at least part of its contents to permeate superposed portions of said elements including said silver halide layer, the portion of said printreceiving element adapted to be permeated by said liquid including a silver precipitation initiator comprising at least one salt from the class consisting of the metallic sulfides and selenides, said salt being dispersed among particles of an inert water-insoluble substance and being aggregated thereby into separate galaxies, said liquid, upon release, rendering said silver halide developer and said silver halide solvent etfective to develop a latent negative image in said silver halide layer and to form soluble silver complexes with the undeveloped 'silver halide in said silver halide layer, said salt initiating and so controlling the precipitation of the silver from said soluble silver complex as to form a transfer image in silyenadjacent the surface of the print-receiving element, .Ea dt mage having improved color and density characer1s ics.

8 l2. .Atphotographicpro'duct capable of forming transfer prints in conjunction with a silver halide element, said product comprising -a rupturable contaimng means holding a liquid, anda sheet support upon 'which'saidcon- =taining means is mounted, said sheet support providing an image-receiving area adjacent said containing means onto'whichsaid liquid is spreadablein a thin layer directly from said containing means, said product carrying a silver halide developer and a silver halide solvent, said image-receiving area of said support including a silver precipitation initiator comprising 'at least one salt from :receiving area to form a transfer print on said imagereceiving area of a latent image contained in an area of :a silver halide clement equivalent to said imagereceiving area.

3. A photographic product capable of 'forming transfer prints in conjunction with a photosensitive silver halide element, said product comprising a rupturable containing means holding an alkaline liquid solution -of a .silver halide developer, a silver halide solvent and an organic film-forming colloid, and a sheet support upon which-said containing means is mounted, said sheet support providing an image-receiving area :adjacent said containing means onto which said liquid solution is spreadable 'in a thin layer directly from said-containing means, said support having distributed, at least throughout said imagevreceiving area, a silver precipitation initiator comprising at least one salt from the class consisting of the metallic sulfide and selenides, said salt being dispersed among .particles of an inert water-insoluble substance and being aggregated thereby into separate galaxies,said solution and .said salt being sufficient in amount so that the spreading of said liquid over said area provides reagents throughout said area in adequate quantity .to form .a transfer print of :a latent image in an equivalent area of a silver .halide element.

4. A photographic product comprising a photosensitive element which includes -a silver halide layer, a printreceiving element which includes aprint-reeeiving layer for receiving a transfer print, and a containing means =releasably holding a liquid, said product having positioned therein photographic reagents including a silver halide developer and a silver halide solvent, said containing means and said elements being so held together that=said containing means is capable of releasing at least-part of its contents to permeate superposed portions of said elements, including said silver halide layer and said printreceiving layer, said print-receiving layer comprising a macroscopically continuous matrix consisting essentially of submacroscopic agglomerates of particlesof a\waterinsoluble, inorganic, chemically inert, adsorbent substance, said particles having a relatively low coeflicient of absorption for light as compared to silver, said matrix having dispersed therethrough a silver precipitating agent for aiding the reduction and precipitation :of metallic silver from silver complex ions in the presence .of 'a developlng agent, said matrix being relatively free .of :protective colloid action for silver, said liquid, .upon release, rendering said silver halide developer and said silver halide solvent effective to develop a'latent imagein said silver halide layer and to form soluble silvercomplexes with the undeveloped silver .halide in said silver halide layer, said silver precipitating agent initiating and so controlling the precipitation of the silver from said soluble silver complex as to 'form a transfer image in silver adjacent the surface of the print-receiving element.

5. A photographic product capable of forming ttransfer prints in conjunction with a silver halide element, said product comprising a containing means holding -a liquid and a sheet support upon which said containing means is mounted, said sheet'support providing'antimagereceiving area adjacent said containing means'onto which saidliquid is spreadable in a thin layer from 'said .con- .taining means, .said product carrying 'a silver halide developer and a silver .halidesolvent, said support having a print-receiving layer adjacent the surface thereof upon which said liquid is to be spread, said print-receiving layer comprising a macroscopically continuous matrix consisting essentially of =submacroscopic agglomerates of 9, particles of a water-insoluble, inorganic, chemically inert, adsorbent substance, said particles having a relatively low coefficient of absorption for light as compared to silver, said matrix having dispersed therethrough a silver precipitating agent for aiding the reduction and precipitation of metallic silver from silver complex ions in the presence of a developing agent, said matrix being relatively free of protective colloid action for silver, said liquid and other reagents being sufficient in amount and being rendered effective by the spreading of said liquid on the image-receiving area to form a transfer print on said image-receiving area of a latent image contained in an area of a silver halide element equivalent to said image-receiving area.

6. A photographic product capable of forming transfer prints in conjunction with a photosensitive silver halide element, said product comprising a rupturable containing means holding an alkaline liquid solution of a-silver halide developer, a silver halide solvent and a film-forming thickening agent, and a sheet support upon which said containing means is mounted, said sheet support providing an image-receiving area adjacent said containing means onto which said liquid solution is spreadable in a thin layer from said containing means, said support having a print-receiving layer adjacent the surface thereof upon which said liquid is to be spread, said print-receiving layer comprising a macroscopically continuous matrix consisting essentially of submacroscopic agglomerates of particles of a water-insoluble, inorganic, chemically inert, adsorbent substance, said particles having a relatively low coefiicient of absorption for light as compared to silver, said matrix having dispersed therethrough a silver precipitating agent for aiding the reduction and precipitation of metallic silver from silver complex ions in the presence of a developing agent, said matrix being relatively free of protective colloid action for silver, said solution and said precipitating agent being suflicient in amount so that the spreading of said liquid over said area provides reagents throughout said area in adequate quantity to form a transfer print of a latent image in an equivalent area of a silver halide element.

7. A print-receiving element for having transfer prints formed thereon by precipitating the silver of a soluble silver complex brought into contact therewith, said element being essentially nonphotosensitive to light and comprising a sheet support having a continuous surface and a thin, silver precipitation layer mounted on said surface, one surface portion of said element, including said layer, being permeable to the ionic content of an aqueous solution of a soluble silver complex, said layer consisting of particles of a water-insoluble, inorganic, chemically inert, adsorbent colloid havig a relatively low coefficient of absorption for light as compared to silver and particles of a silver precipitating agent for aiding the reduction and precipitation of metallic silver from silver complex ions in the presence of a developing agent, said matrix being relatively free of protective colloid action for silver, said silver precipitating agent being present in said silver precipitation layer in a substantially lesser concentration than the said colloid and being aggregated by the colloid of said layer into galaxies which exhibit low optical densities when said layer is viewed macroscopically, said silver precipitating agent being zinc sulfide.

8. A print-receiving element for having transfer prints formed thereon by precipitating the silver of a soluble silver complex brought into contact therewith, said element being essentially nonphotosensitive to light and comprising a sheet support having a continuous surface and a thin silver precipitation layer mounted on said surface, one surface portion of said element, including said layer, being permeable to the ionic content of an aqueous solution of a soluble silver complex, said layer consisting of particles of a substance from the class consisting of bentonite and fullers earth, said layer having dispersed therethrough particles of a substantially waterinsoluble silver precipitating agent, said silver precipitating agent being present in said silver precipitation layer in a substantially lesser concentration than the said sub stance and being aggregated by said substance into galaxies of low optical density.

9. A photographic product comprising, in combination, a photosensitive element, including a silver halide emulsion, and a print-receiving element mounted in supe rposed relation with said photosensitive element, said print-receiving element being essentially nonphotosensitive to light and comprising a thin silver precipitation layer adjacent the silver halide emulsion of said photosensitive element, said layer comprising particles of a substance from the class consisting of bentonite and fullers earth and, in lesser concentration, particles of a substantially water-insoluble silver precipitating agent for aiding the reduction and precipitation of metallic silver from silver complex ions in the presence of a developing agent.

1 0. The product of claim 9 wherein the silver preclpi tatmg agent is at least one salt from the class consistlng of the metallic sulfides and selenides.

11. A print-receiving element for having transfer prints formed thereon by precipitating the silver of a soluble silver complex brought into contact therewith, said element being essentially nonphotosensitive to light and comprismg a sheet of baryta paper as a support, and a discrete thin silver precipitation layer mounted upon the baryta-coated surface of said support as a separate layer from the baryta coating of said support, one surface portion of said element including said layer being permeable to the ionic content of an aqueous solution of a soluble silver complex, said layer consisting essentially of particles of a water-insoluble, inorganic, chemicallyinert, adsorbent colloid, said particles having a relatively low coefficient of absorption for light as compared to silver, said layer having dispersed therethrough particles of a substantially Water-insoluble silver precipitating agent for aiding the reduction and precipitation of metalllc silver from silver complex ions in the presence of a developing agent, said particles of silver precipitating agent being present in said silver precipitation layer in a substantially lesser concentration than the said particles of colloid and being aggregated by the colloid of the sa d layer into galaxies which exhibit low densities when said layer is viewed macroscopically.

12. A print-receiving element for having transfer prints formed thereon by precipitating the silver of a soluble silver complex brought into contact therewith, said element being essentially nonphotosensitive to light and comprising a sheet support having a continuous surface and a thin, silver precipitation layer mounted on said surface, one surface portion of said element, including said layer, being permeable to the ionic content of an aqueous solution of a soluble silver complex, said layer consisting of particles of a water-insoluble, inorganic, chemically inert, adsorbent colloid having a relatively low coefiicient of absorption for light as compared to silver and particles of a silver precipitating agent for aiding the reduction and precipitation of metallic silver from silver complex ions in the presence of a developing agent, said matrix being relatively free of protective colloid action for silver, said silver precipitating agent being present in said silver precipitation layer in a substantially lesser concentration than the said colloid and being aggregated by the colloid of said layer into galaxies which exhibit low optical densities when said layer is viewed macroscopically, said colloid being at least one substance from the class consisting of bentonite and fullers earth.

13. The process of forming positive images in silver which comprises developing a latent negative image in a silver halide layer, reacting a silver halide solvent with part at least of the undeveloped silver halide of said layer to form an imagewise distribution of soluble silver complex in said layer, transferring, in solution, at least part of said imagewise distribution of said soluble silver complex to an image-receiving material so located in relation to said silver halide layer as to receive the solution of said complex without appreciably disturbing its imagewise distribution, and reducing to silver the silver ions of said complex in the presence of a silver precipitating agent contained in said image-receiving material for aiding the reduction and precipitation of metallic silver from silver complex ions, said precipitating agent being substantially insoluble in said processing liquid and being dispersed throughout a macroscopically continuous matrix consisting essentially of particles of a water-insoluble, chemically inert, adsorbent, inorganic colloid from the class consisting of bentonite and fullers earth, said particles having a relatively low coefficient of absorption for light as compared to silver, said silver precipitating agent being aggregated by said matrix into, galaxies of low optical density.

References Cited in thefile-of thispatent Number UNITED STATES PATENTS Name Date Trotter May 8, 1883' Thorp May 10, 1887 Eichengrun Oct. 27, 1903; Poetschke Sept. 3, 1918 Van Der Grinten Jan. 19, 1932 Walker Sept. 26, 1933- Schmidt Apr. 24, 1934 McIntosh Apr. 21, 1936 Happel et al. Dec. 21, 1937 Sheppard Dec. 19, 1939 Schwartz, Mar. 25', 1941 Schaefer Dec. 2, 1941 Knott Apr. 6, 1943 Crowley et a1. Apr. 27, 1943 Rott June 20, 1944v Number.

Name. Date: Gary: Mar; 25, 194 7: Bloom Aug; 26,1947? Johoda Dec; 30,, 1947. Land ,,Feb-.,27, 195:1;

FOREIGN PATENTS Country Date,- France; June 30,1941: France, Dec. 10, 1942; Germany V Oct. 10; 1923.

OTHER REFERENCES Photographic Rundschau, vol..,6,-1;, gpz 59; 19.24. Mees, The Theory, of; the Photographic; Process,

published by. The-Macmillan. Company, New York; 1942,, pages 9396 and; page: 162. I

Wall, Photographic; Emulsions? published; by. Amelie can Photographic Publishing Comp anY,,Boston (1929),,- go, pages, 247-253.

Stevans; and Norrish; Rhotographic; Journal" (.Great: Britain), 1938, No. 38, pp. 5 2,4. particularly pertinent: 

1. A PHOTOGRAPHIC PRODUCT COMPRISING A PHOTOSENSITIVE ELEMENT WHICH INCLUDES A SILVER HALIDE LAYER, A PRINTRECEIVING ELEMENT FOR RECEIVING BY TRANSFER A POSITIVE PRINT, AND A RUPTURABLE CONTAINING MEANS HOLDING A LIQUID, SAID PRODUCT HAVING POSITIONED THEREIN PHOTOGRAPHIC REAGENTS INCLUDING A SILVER HALIDE DEVELOPER AND A SILVER HALIDE SOLVENT, SAID CONTAINING MEANS AND SAID ELEMENTS BEING SO HELD TOGETHER THAT SAID CONTAINING MEANS IS CAPABLE UPON RUPTURE, OF RELEASING AT LEAST PART OF ITS CONTENTS TO PERMEATE SUPERPOSED PORTIONS OF SAID ELEMENTS INCLUDING SAID SILVER HALIDE LAYER, THE PORTION OF SAID PRINTRECEIVING ELEMENT ADAPTED TO BE PERMEATED BY SAID LIQUID INCLUDING A SILVER PRECIPITATION INITIATOR COMPRISING AT LEAST ONE SALT FROM THE CLASS CONSISTING OF THE METALLIC SULFIDES AND SELENIDES, SAID SALT BEING DISPERSED AMONG PARTICLES OF AN INERT WATER-INSOLUBLE SUBSTANCE AND BEING AGGREGATED THEREBY INTO SEPARATE GALAXIES, SAID LIQUID. UPON RELEASE, RENDERING SAID SILVER HALIDE DEVELOPER AND SAID SILVER HALIDE SOLVENT EFFECTIVE TO DEVELOP A LATENT NEGATIVE IMAGE IN SAID SILVER HALIDE LAYER AND TO FORM SOLUBLE SILVER COMPLEXES WITH THE UNDEVELOPED SILVER HALIDE IN SAID SILVER HALIDE LAYER, SAID SALT IMITIATING AND SO CONTROLLING THE PRECIPITATION OF THE SILVER FROM SAID SOLUBLE SILVER COMPLEX AS TO FORM A TRANSFER IMAGE IN SILVER ADJACENT THE SURFACE OF THE PRINT-RECEIVING ELEMENT, SAID IMAGE HAVING IMPROVED COLOR AND DENSITY CHARACTERISTICS. 